The Biological Effects of Nuclear War

Paul R. Ehrlich, 1984

Paul R. Ehrlich, an insect biologist, is Bing Professor of Population Studies at Stanford University. He is a leader in the international crusade for ecological awareness and population control. His many honors and awards include election to Fellowship in the American Association for the Advancement of Science and The John Muir Award of the Sierra Club. In elaborating his concern about the effects of nuclear war on the environment, he reminds us that few problems are less recognized but more important than the accelerating disappearance of Earth's biological resources.

Whiteley: Professor Ehrlich, what are the effects on the basic ecology system of nuclear weapons?

Ehrlich: Well, if it's a full-scale nuclear war (and I think most people are convinced that if there is a nuclear war it will be full-scale; that is most military analysts) there are likely to be very serious changes in the atmosphere caused by putting a lot of soot from the widespread fires that will be started into the lower part of the atmosphere, and a lot of dust into the upper part of the atmosphere. That is going to intercept the light that normally, first of all drives all ecological systems through the process of photosynthesis, and also warms the surface of the Earth. So we're going to have a situation in which it will be very cold and very dark on the surface, particularly in the continents. And that's what's been called a nuclear winter. And what a nuclear winter will do - just those two effects, although there will be many others along with it - will be essentially to knock out all of agriculture, to severely damage natural ecological systems, and essentially wipe them out temporarily (they will eventually come back and kill any human survivors, at least in the Northern Hemisphere). So basically the roughly half of humanity that will be killed outright in a large-scale nuclear war will be followed by almost certainly the deaths of all the people, at least in the Northern Hemisphere. And it is not even impossible that all humanity could be wiped out if the effects spread widely enough to the Southern Hemisphere.

Whiteley: You said it might be limited to the Northern Hemisphere. What is the reasoning behind that?

Ehrlich: Well, first of all, most people who look at targeting believe that the vast majority of targets are in the Northern Hemisphere. Therefore, most of the war would occur in the Northern Hemisphere. So the basic scientific question which the atmospheric physicists have not yet been able to satisfactorily answer is how much will the soot and dust spread from the Northern to the Southern Hemisphere? How severe will those conditions get if there is a nuclear winter in the Southern Hemisphere; how bad will it be? I don't think, I led a group of biologists looking at the results of the atmospheric physicists' studies - and we concluded that it was very unlikely that all human beings in the Southern Hemisphere would be wiped out at once, but we thought it was quite possible if the effects spread in large part to the Southern Hemisphere that there would be just scattered groups of survivors in places like oceanic islands and along shorelines, and they would be facing extremely unusual conditions, ecological conditions. Their social structure would be very badly disturbed, their economic situation would be horrendously changed, they would have difficulty farming, they might be inbred subject to high levels of radiation, and it was not clear to us that they would recover and repopulate the planet. It seemed also possible that they would dwindle away and our species would become extinct.

Whiteley: Because we would go below whatever critical number it is to perpetuate a species.

Ehrlich: That's right. You need, well among other things, you'd normally need more just than one male and one female to get things going again. You have to have a certain store of genetic variability in any species, normally, to be able to rebuild from what we call a narrow bottleneck. If your bottleneck population does not come out into normal ecology, if your very small population does not then face normal ecological conditions for that species, then the chances that it will go extinct become very much larger, and what we do know from the studies that have been done so far is that the ecological conditions for human beings - and I'm talking here both the natural ecology if you will, the social ecology would be extraordinarily different and that's why we think there's a possibility, at least, that a large-scale nuclear war could end with the extinction of Homo Sapiens.

Whiteley: Let's start with the nuclear winter that you talked about and the impact on the surface of the Earth was two, an interference with photosynthesis and an interference with the warming that naturally occurs from the sun. What's going on up there in the atmosphere that is causing that to occur, and how long do you think that that would persist?

Ehrlich: Well, of course, it depends on the exact season, the distribution of the weapons, whether they're exploded close to the ground or higher in the atmosphere - all those things will affect what goes on. But basically you'll have a dust layer in the stratosphere which will tend to reflect solar energy and a soot layer in the so-called troposphere (that's the mixed lower portion of the atmosphere). That's not necessarily all that low; it can be several miles up, which will be greatly warmed by absorbing the solar energy. And the solar energy that is absorbed in the troposphere, or reflected away from the stratosphere, will of course not warm the surface of the Earth. So for instance, it is quite possible, it is conceivable that in Kansas in the month of July, it could be 45os below zero Fahrenheit, and also dark. And that the darkness would last for weeks and the temperature could be way down for a matter of weeks, down for a matter of months. In other words for instance, you could possibly be below 0o over much of the Northern Hemisphere land surface for three or four months. And it could be cooler than normal for a year or more, so you're talking about a rather prolonged episode, but all these effects would be accompanied by much higher than previously thought levels of radiation, hemispheric smog, and when things did settle out of the atmosphere by a flux of so-called UVB, a dangerous wave-length of ultraviolet light that is normally screened out by the Ozone layer, but the Ozone layer would be disrupted - itself would be disrupted by the war.

So you have all of those effects, plus other ecological effects, and it really doesn't matter very much how accurate the physicists predictions are because in the biological system the overkill is horrendous. In other words, turning out the lights for a few days would be awful. Taking the temperature down just to 0o in the middle of the summer for a relatively few hours would be horrendous for biological systems. I mean when you're talking about taking it below 0o - way below 0o for weeks and turning out the lights basically for weeks, then the level of overkill is such that you don't really have to worry about the other effects. If you don't believe it, you can run a little experiment in your very own house. Take your African Violet and throw it in the freezer overnight, just for 12 hours, and then bring it out and try to revive it with mouth-to-mouth resuscitation and see what happens. In other words, plants don't get along in very cold temperatures without light.

Whiteley: So one consequence is the consequence of change in the atmosphere; the second consequence is the consequence in the change in temperature on the surface. You've written about the changes in the fresh-water regulation system.

Ehrlich: Oh sure, well you see when all these things go on, you of course change precipitation patterns which would have a serious effect on any surviving animals. The people who are trying to get along in these conditions would find it very difficult to get fresh water because when you take it down to 30o or 40o below zero, of course all the surface waters freeze to several feet deep, and all the pipes freeze up and so on, so that in many areas, people, if they were not dead or radiated - of blast, of radiation, of burning of fires, of choking in the smog, of freezing to death or starving to death would die of thirst. In other words, the number of assaults that people would have to face, we would be in a situation unprecedented worse than the survivors of Hiroshima. After the bomb went off at Hiroshima, a single bomb, and the fire ended, then not only was there sunlight, but they were surrounded by undisturbed islands basically, with other people who could come in and help them. Whereas survivors in the Northern Hemisphere after the war is over, after the first few hours, are going to be trying to find help in a smoggy, cold, dark world. They're going to be stumbling around in the dark. There aren't going to be electric lights, for instance, to help you out. So it's going to be horrendous and the problem of finding medical aid for the victims is going to be insurmountable, and my guess is that if you have a full-scale war, that within a month, essentially, everybody in the Northern Hemisphere will be dead. There may be a few survivors in very deep, very well-stocked shelters, but there will be nothing for them to do when they come out. They'll mostly serve as food for cockroaches and rats that are likely to survive the war much better than human beings.

Whiteley: What are the implications for the soil system?

Ehrlich: What happens to the soil is going to depend a lot on the distribution and intensity of fires. One of the things we know very little about is under what conditions one can get fire storms that can sterilize the soil. But the general effect is going to be for huge areas to be burned off. For example, if a war should occur, say in September, one would expect California to burn from end to end. The brush fires that one normally sees on the TV news occurring in Los Angeles caused by a few juvenile delinquents playing with matches will be nothing compared to, let's say 15 or 20, 40 to 80 kiloton thermonuclear weapons going off over the Los Angeles basin would be. So all the chaparral would burn up and down the coast, the interior grasslands would be bone dry and burn, the forest would burn. So they would be contributing to this blanket of smog of smoke that would blank out the sun over the Northern Hemisphere. At the same time, of course, the soil would be dinuded. Where the fuel loadings were sufficiently large, and the conditions were right, the soil would be sterilized. And then, after conditions return to "normal," you would have your winter rains, and the winter rains would simply wash the soil into the oceans, both getting rid of the soil in large part, but also killing off any oceanic life that matters to survive the nuclear winter along the coast, because silting is a very serious assault on oceanic ecosystems. So soil systems would be badly damaged, and would recover only very slowly, if you had widespread fires because, of course, the source of seeds and so on, it is necessary to re-establish. Normally we'd have a burned area - say trees in adjacent areas that produce seeds that blow in and help re-establish the forest. It's not all from the soil bank of seeds, but of course, in most cases, there would be no adjacent areas to help with the revegetation to hold the soil in place.

Whiteley: What about the cycling of wastes?

Ehrlich: The cycling of wastes would be one way basically, because the organisms that normally help recycle wastes would disappear, and so what would happen is that most wastes would simply flow into the sea, or a lot of decomposition of bodies and so on - well, it would depend exactly on the conditions, but you would have probably an awful lot of dead people lying around in areas, an enormous potential source of disease if there were any survivors to catch the disease. But in general, the services that we normally get from ecological systems, as like you mentioned earlier the cycling of water, the control and metering of water, which is done so beautifully by forests, and by deep soils, and so on. The generations of soils, the maintenance of soils, the recycling of wastes, the provision of food from the sea - all of those things would simply be interrupted or ended totally from the point-of-view of any surviving human beings.

Whiteley: Pest and disease control is another feature that you've written about. What are you trying to share there?

Ehrlich: Well, basically the kinds of organisms that will do best in a nuclear winter - the ones that survive easiest - will be the ones that are normally considered to be pests. That is, organisms that are able, like houseflies, and cockroaches, and rats, that have enormous reproductive potential, that are able to feed on a wide variety of things, including bodies and debris, and dead plants and so on - they vary from organism to organism. So one would expect to find human beings that survived would be facing an ecosystem that would be greatly modified in the direction of having the sorts of organisms in it that people normally think of as pests and weeds. Now, after a nuclear war the disease situation may very well not be severe, because, in the terms of contagious disease, there won't be anybody to catch it from. But in terms of whether you will be assaulted by pests - in other words I would say a very likely thing to happen to survivors of a nuclear war would be to be eaten by rats, which most of you know, could be very nasty and large if they become very prominent. Just think that you're going to have in North America, for example, more than two hundred million dead human bodies, and several times that, dead large animal bodies, and that's going to make an enormously rich breeding ground for any surviving animals like rats or cockroaches that can survive on that sort of thing.

Whiteley: Well, I suppose it will depend on the time of year that a nuclear war would occur, the effects on the food supply system must be quite major.

Ehrlich: Well, the effects on the food supply system would probably be lethal whenever a war occurs. For the simple reason if the war occurs after the harvest, there will still, of course be, the harvest of food, but most of that will be concentrated in areas where it will be destroyed in the war. And then what the nuclear winter will mean, if it starts in the winter, is a much colder than usual winter, but more important a winter that stretches on into the normal springtime when planting would occur and plants would be sprouting, and so on. Actually, many plants are more susceptible to damage when they're first sprouting, when they're first putting out leaves and so on. Animals that have, for instance, barely gotten through the winter on their stored reserves have to start-up in the spring and feed fast, or they die. And so, say a February war or something, or a January war might have a smaller immediate effect on plants and animals in the colder areas of the Northern Hemisphere. But as those animals and plants attempted to survive longer than usual in cold conditions, they would die.

And remember most of the Northern Hemisphere is not frozen even in January or February. I mean we've got to remember there's a lot of tropics in the Northern Hemisphere and the impact there may be even worse because it may spread cold deeper into the tropics. So it's true we don't know much about the seasonal differences, and the overall effects might be slightly less, say, if we had an absolute optimum war. Let's suppose that the ideal time to have a thermonuclear war from the point-of-view of seasons in the Northern Hemisphere, let's say was early December after winter had set in, but as far as possible from the spring. Then maybe instead of having - I'll make up a number - 4 billion deaths in the Northern Hemisphere, you might only have 3.95 billion deaths in the Northern Hemisphere. In other words, there might be more survivors, but you're talking basically about nonsense because the survivors won't have anything to do. I think it's important for people to realize - I will assert that you could destroy the United States as a functioning entity with 20 Hiroshima-sized atomic bombs. That is, you could destroy the centers; basically destroy the 20 largest cities in the United States. If you make a list to try and figure out what the country would be like after that, I think most people would be convinced it would not be the America that we know. That's 20 Hiroshima-sized bombs. Now, compare that with the size of the strategic arsenal today, and it's likely to get bigger with cruise missiles, but compare that to the size of the strategic arsenal today.

A friend of mine during the nuclear winter two-day meetings that were held around Halloween of 1983, calculated how many Hiroshima-sized bombs could be detonated per hour in order to use up the ten thousand megatons worth of weapons that are in the strategic arsenals. That is, how many Hiroshimas are there there, scaled as how many detonations would you have to have per hour to use them up in 48 hours. The answer is six a second. We have enough - we could create six Hiroshimas a second for 48 hours in the Northern Hemisphere. And that will give you some measure of what kind of power is out there, and what the world would be like for any survivors that just happen not to be killed in this enormous holocaust. Just sit down for a few minutes, and try to picture those few minutes having been six giant cities disappearing, because a Hiroshima-sized bomb is quite enough to ruin any city. I mean sure, there will be survivors and the peripheral areas won't be damaged, but a Hiroshima going off downtown pretty much takes care of downtown anywhere. Los Angeles might be the example that doesn't hold that, because Los Angeles is so spread out. But even a single Hiroshima-sized bomb in Los Angeles: would create a mess beyond all belief. And yet, six a second - that means you'd take care of the United States in over three seconds. Less than four seconds to destroy the United States and you've got 48 hours to go. So, I think it's really silly to focus on what might happen to a few survivors.

Whiteley: You've written that one effect of a nuclear war would be on the genetic library. What are you trying to share with us?

Ehrlich: Well, people have to understand that humanity has already withdrawn the very basis of its civilization from what people have described as the genetic library of the planet. That is the population and species of other organisms with whom we share the Earth, and there are as many as 30 million other species - we're not really sure - and billions of populations of those species. For instance, all of our foods come from the various animals we've domesticated, the various plants that we've domesticated. Something like a half of all the prescriptions that are written in the United States today contain as their active ingredient either a biochemical taken from a plant, or one designed on the model of a biochemical that has been taken from a plant. We use a vast number of industrial products that come from plants and animals. For example, every time you land in a jet airliner there is natural rubber in the tires because chemists have not been able to synthesize an artificial rubber that has the thermal characteristics of natural rubber.

So you have this enormous diversity out there, and yet a nuclear war is going to destroy a vast majority of it. It's going to be an event like some people now think killed off the dinosaurs and many other organisms sixty-five million years ago. It's going to wipe out - because of killing off so many plants and the animals that are utterly dependent on the plants - it's going to remove a vast portion of the diversity of organic beings on the planet. Now, it's quite true that there will be survivors and that 65 million years after the war, diversity will undoubtedly have been regenerated, but in a very different form. That's not going to mean very much to the people, if they survive, for the few centuries after the war, when you have to, in order to regenerate organic diversity, get new species. For instance, you're talking about hundreds of thousands or millions of years to even start. So what you're going to lose is all of the aid we now get from those organisms, and the potential for withdrawing more. There is an enormous potential for doing more. We've barely scratched the surface of domestication. Only about thirteen animals are really significantly domesticated out of many hundreds of thousands, and if you look at crops, only about 25 or 30 crops are really significant internationally, and there are only about 200 altogether out of something like 250,000 species of higher plants. If we wipe them out, the potential for getting new foods, new drugs, and so on just becomes zero.

Whiteley: You've been very clear about the effects on the ecology of our world of nuclear weapons. You've also thought very carefully about what our society needs to do differently to avert that, to achieve some kind of enduring peace. What do you see the role of government to be in achieving peace?

Ehrlich: Well, I would like to think the role of government would be leading in the right direction. Unfortunately, in our country, I think we have to count on the people doing the leading and the government following. I think from a biologist's point-of-view, the key point is that human beings living in states - in national states - and having large-scale wars with each other is a brand new phenomena. In other words, it's occurred only within the last ten thousand years, and actually much more recently than that - only since the agricultural revolution. There is nothing that says that human beings have to have large-scale wars with each other. And many societies have lived without that, and even today for instance, North America, the United States and Mexico and Canada have shared North America without a large-scale war since 1849, I guess. So it is possible to live at peace with one another, but I think the crucial point is that we no longer have any choice. In other words Clausewitz is stone cold dead and people just don't realize it. War - large-scale war - can no longer be used as an extension of politics, because even if you completely control nuclear weapons it won't do any more because even the Second World War fought again today in a world with twice as large a population, in a world where now there's only one major area that is a dependable food exporter; whereas when the second world war was fought every area but one was a major food exporter. The disruption of just a plain old Second World War today would cause it to be infinitely worse than the Second World War, which as I remember very well was an indeed a horror. And besides, if you had a Second World War again, we would just have - even if you had gotten rid of nuclear weapons - you would just have a new nuclear arms race. We had nuclear weapons in the Second World War when we didn't know how to make them at the beginning, and we had them at the end. So basically the thing people have to recognize is that there simply is no choice. We cannot afford large-scale wars, period. And once people realize that, then maybe the politicians and the people, can just begin looking differently in all nations at the problem.

Whiteley: What's the role of religion in that?

Ehrlich: Well, I think there is a number of roles that religion can play on this. One is to make sure that human beings not only respect their co-religionists, but all human beings, and most great religions have that message. They don't have the message of respecting the planet, and I think that's very important to understand that we are all wrapped up on this tiny little planet with very fragile life support systems, and while it's very important we respect each other, we also have to respect the planet, because it's disrespect for the planet, among other things, that is leading to many of the battles that we're now having over resources for example. In other words, the reason the Straits of Hormuz are in the news all the time should be clear. People are prepared to go to war to protect a resource, and the reason that resource needs protection is that people have been abusing the planet hideously. All the great religions have to point out that it is far past time that we gradually lower our birth rate below the death rate, keeping the death rate as low as possible, and begin to reduce our population size to a size where all people can live happily and healthily on the planet. If we don't do that, we're just out of luck.

Whiteley: What do you see the role of education to be?

Ehrlich: Well I think that there's nothing more important. I think that it's sad - I'll speak only for the United States now - but the average American has no notion of the scale of the nuclear arsenals. If they did, they would laugh hysterically when any president of any party said that we need more nuclear weapons. Again, I say think about it: six Hiroshimas a second for 48 hours - that's a lot of deterrence when we should be more than enough deterred with a couple of nuclear weapons per nation. Most people in the United States don't have even the simplest technical background to allow them to understand a world that is being more and more ruled by technology. Our science education is terrible. They don't understand the way we're dependent upon the environment. I think there's nothing more important than shifting our education system to focus first of all on the very basics. You cannot learn about how the world works unless you can read and write and do arithmetic. But also to focus more on what is important to understand about how our social systems work, about how our economics work, and about how we relate to each other and to our environment.

Whiteley: Both you and I spend our time in universities, yet universities have been very slow in putting in their curricula courses on peace. Why is that?

Ehrlich: Well I've often said that if people think the church is conservative, they should try a university. They're like any other large bureaucratized system; they've got to be moved by the people inside the university, and they are strangled by the same kind of bureaucratic and financial concerns that really affect businesses and the government and society as a whole, and this is a place where we try very hard at the universities to stay ahead, but it's a very tough job, and we haven't done enough. That's all. It's part of the same general educational process. So what you're going to do in the universities is fight to get innovation, because they claim to be innovators. If you look at universities, though, they aren't in general.

Whiteley: And part of the reason is, as you're explaining it, that both ecology and peace are issues that you have to look at from an interdisciplinary perspective, and universities aren't set up to do that very well.

Ehrlich: Well, that's about an hour and a half discussion about what business should do differently, but I think that business, like the universities, has to realize that a businessman's responsibilities are not just directly to the people who own the business, to the stockholders. It is the role of business executives to lead, to see to it, for example, the stockholders' children get a chance to live decent lives, too.

Whiteley: Professor Ehrlich, thank you for sharing with us today your insights into the effects on the ecology of nuclear war, and your insights on the ways we need to live differently to achieve peace in the world.